1. Field of the Invention
The present invention relates to a gas turbine apparatus, and more particularly to a gas turbine apparatus for use in a micro gas turbine power generation apparatus or the like.
2. Description of the Related Art
A conventionally-known gas turbine apparatus generally comprises an air compressor for compressing air, a combustor for combusting the air compressed by the air compressor, a turbine rotated by receiving a combustion gas generated in the combustor, and a recuperator for heating the compressed air to be supplied to the combustor using heat of an exhaust gas discharged from the turbine.
Applications of gas turbine apparatus of this type include a micro gas turbine power generation apparatus. This micro gas turbine power generation apparatus has a very small-sized turbine and a very small-sized generator coupled to the turbine. A combustion gas is supplied to the turbine to thereby rotate the generator at a high speed, e.g., about 100,000 revolutions per minute. Although the micro gas turbine power generation apparatus is very small in size, it can generate about, for example, 50 to 100 kW of electric power. Hence, the micro gas turbine power generation apparatus has recently received remarkable attention as one of geographically-distributed power sources.
Japanese laid-open patent publication No. 2003-322030 discloses a gas turbine apparatus having a triple pipe which forms three flow passages: a flow passage for providing fluid communication between an air compressor and a recuperator; a flow passage for providing fluid communication between the recuperator and a combustor; and a flow passage for providing fluid communication between a turbine and the recuperator. FIG. 7 shows a perspective view of the triple pipe structure disclosed in the above-mentioned Japanese patent publication. In FIG. 7, air is compressed by an air compressor and is introduced into a recuperator 115 through an outer passage 124 and a connection pipe 127. The compressed air, heated by the recuperator 115, is then introduced into an intermediate passage 125 through compressed-air outlets 129 and introduction pipes 128 each having a semicircular cross section. An exhaust gas is discharged from a turbine, and is introduced into the recuperator 115 through an inner passage 126.
As shown in FIG. 7, the compressed air, flowing through the outer passage 124, strikes a front surface 115a of the recuperator 115, whereby the compressed air changes its direction and flows into the connection pipe 127. However, the introduction pipes 128 extend across the outer passage 124, and hence part of the compressed air is intercepted by the introduction pipes 128, which disturb smooth flow of the compressed air from the outer passage 124 toward the connection pipe 127. As a result, the compressed air is placed in contact with the high-temperature introduction pipes 128 and the high-temperature front surface 115a of the recuperator 115 for a long period of time, and a temperature of the compressed air is thus increased. Further, upon striking of the compressed air against the front surface 115a, the compressed air would be heated by this high-temperature front surface 115a. 
Such an increase in temperature of the compressed air results in a decrease in efficiency of heat exchange at the recuperator 115 into which the compressed air flows subsequently. More specifically, in the recuperator 115 that serves as a heat exchanger, the lower the temperature of the compressed air to be introduced into the recuperator 115, the greater an amount of heat transferred from the exhaust gas to the compressed air. Accordingly, the increase in temperature of the compressed air that is to be introduced into the recuperator 115 leads to the decrease in efficiency of the heat exchange, resulting in a lowered amount of exhaust-heat recovery at the recuperator 115.